The present disclosure is related to methods of predicting relative humidity (RH) sensitivity in xerographic developer materials. In particular, the RH sensitivity of xerographic developer materials is established by calculating a Lewis acid-base RH ratio.
Humidity levels contribute to the overall print quality and performance in printing devices, such as ink jet printers, ionographic printers, laser printers, and copiers. These levels vary from model to model and, depending upon the moisture content in the media and in the air, they will directly affect print quality and performance. Some of the most frequent problems in a printing device can be caused by high RH conditions (e.g., hot, wet weather) or low RH conditions (e.g., cold, dry weather). Print quality defects common to low levels of RH can include: light or faded prints, washed-out prints, light areas of banding, and reoccurring text on the same page. Print quality defects common to high levels of RH can include: excessive background, over-saturation of color content and areas of offsetting where the toner peels off the page.
It is well known that tribo-electrification is strongly influenced by RH. For example, emulsion aggregation (EA) polyester toner particles are very hydrophilic, and thus may experience unpredictable tribo-electric charging upon exposure to atmospheric humidity. More in particular, EA polyester toners have hydrophilic functional groups on the surface of the toner, causing humidity sensitivity. At low RH, the toner tribo-electric charge may be higher in charge magnitude and at high RH the toner may be lower in charge magnitude. Such toner particles thus may need to be treated, for example with a hydrophobic agent, in order to perform over a wide range of humidity conditions.
Currently, there is no way to predict RH performance in xerographic developer materials. Improvement of charging performance with RH, that is, finding toners with desirable RH sensitivity, is largely trial and error, which is not only timely and costly, but may not produce the best results.